Here’s an easy one. If space is nothing and time is a concept, what is space time?
It's not what we would call normal like something we can touch and feel. Ancient times thought you kinda could and called it the Ether, and other names.I believe space is a thing. Did it become something more than nothing, meaning does space now have mass?
A coordinate system is like a mapping plan. Variations in the density of matter (and energy) change the landscape from something, say, flat to regions with dimples, large and small. The analogy of putting a bowling ball on a trampoline is often used where the depression in the rubber sheet represents how the map, or coordinate system, can be used to properly take us from a simple, and incorrect, Cartesian X-Y grid and give us something that can help us produce correct results, such as acceleration rates through it. The spacing between the lines drawn represent the gradient -- the change in the rate of lines encountered with distance.I understand space-time to be like a coordinate system. Am I misunderstanding?